ice ages

For decades, climate scientists have tried to explain why ice-age cycles became longer and more intense about 900,000 years ago, switching from 41,000-year cycles to 100,000-year cycles. In a new study in the leading journal Science, researchers found that the deep ocean currents that move heat around the globe stalled or even stopped, possibly due to expanding ice cover in the north. The slowing currents increased carbon dioxide storage in the ocean, leaving less in the atmosphere, which kept temperatures cold and kicked the climate system into a new phase of colder but less frequent ice ages, they hypothesize.

Gerardo Iturrino, a longtime engineer and ocean explorer at Lamont-Doherty Earth Observatory, passed away unexpectedly on March 12. A resident of nearby Nyack, he was 51; the cause was heart attack, said his family.

In something as tiny as a speck of dust lies the potential to change earth’s climate. When winds blow iron-rich dust off the continents, they give the plant-like algae floating on the surface of the oceans added nutrients to grow faster. Large algal blooms can draw down carbon from the atmosphere, and in extreme cases, cool earth’s climate. Researchers are trying to understand to what extent dust, by providing extra food for algae, or phytoplankton, may have helped to tip the planet into a deep freeze starting about 30,000 years ago. From the onset of the last ice age to its peak, about 18,000 years ago, carbon dioxide levels fell by about 100 parts per million. As much as 25 percent of that drop can be attributed to the effect of dust.

A climate scientist who has suggested how mountain building can lower Earth’s thermostat and why ice ages sometimes wax and wane at different speeds has been awarded one of geology’s oldest and most coveted prizes: the British Wollaston Medal. The first woman to win a Wollaston in the prize's183-year history, Maureen Raymo, a researcher at Columbia University’s Lamont-Doherty Earth Observatory, joins the company of Victorian giants Charles Darwin and Louis Agassiz, and major 20th-century figures including climatologist Sir Nicholas Shackleton and James Lovelock, originator of the Gaia hypothesis. Raymo, 54, will receive the medal, cast in the platinum-like metal palladium discovered by Henry Wollaston in 1803, at the Geological Society of London’s annual meeting in June.

As the last ice age was ending, about 13,000 years ago, a final blast of cold hit Europe, and for a thousand years or more, it felt like the ice age had returned. But oddly, despite bitter cold winters in the north, Antarctica was heating up. For the two decades since ice core records revealed that Europe was cooling at the same time Antarctica was warming over this thousand-year period, scientists have looked for an explanation.

Researchers have reconstructed atmospheric carbon dioxide levels over the past 2.1 million years in the sharpest detail yet, shedding new light on its role in the earth’s cycles of cooling and warming.